1. Field of Invention
The invention relates to a fluid pressure control device for a lock-up mechanism so as to perform a lock-up control of a torque converter that is mounted on a vehicle such as an automobile.
2. Description of Related Art
There exists torque converters that are mounted on a vehicle that include a lock-up clutch. When the lock-up clutch operates, a revolution of an output shaft of an engine that was transmitted to an input shaft of a transmission via fluid in the torque converter is directly transmitted to the input shaft of the transmission via the lock-up clutch. Therefore, fuel efficiency is improved.
The lock-up clutch is operated normally by an engagement pressure based on a line pressure that is generated by a mechanical oil pump. The maximum fluid pressure (supply limit fluid pressure) that is generated by the mechanical oil pump is determined by the rpm of the engine. That is, the supply limit fluid pressure is high when the rpm is high while the supply limit fluid pressure is low when the rpm is low.